Time Division Multiplexing Technology Research Articles

Low-cost lightweight-client twin-field quantum key distribution network with wavelength division multiplexing

In recent years, quantum communication technology has gradually entered the practical stage. Multiple quantum key distribution (QKD) networks have been built and tested all over the world. However, quantum communication networking mode always evolves from a point-to-point network to a many-to-many network. The major challenges in quantum communication are secret key rate, distance, cost, and size of QKD devices. We proposed a low-cost, lightweight-client, twin-field QKD network with wavelength division multiplexing (WDM). The proposed implementation adopts polarization multiplexing, time-division multiplexing, and WDM technology to solve all these major challenges and implement a many-to-many dynamic communications network. Furthermore, our scheme can effectively reduce the cost to less than half of that of current QKD networks and has reference significance for large-scale deployment of QKD networks.

Development of an Online Detection Setup for Dissolved Gas in Transformer Insulating Oil

The type and concentration of dissolved gases in transformer insulating oil are used to assess transformer conditions. In this paper, an online detection setup for measuring the concentration of multicomponent gases dissolved in transformer insulating oil is developed, which consists of an oil-gas separation system and an optical system for acquiring the transformer status in real time. The oil-gas separation system uses low pressure, constant temperature, and low-frequency stirring as working conditions for degassing large-volume oil samples based on modified headspace degassing. The optical system uses tunable diode laser absorption spectroscopy (TDLAS) to determine the gas concentration. Six target gases (methane, ethylene, ethane, acetylene, carbon monoxide, and carbon dioxide) were detected by three near-infrared lasers (1569, 1684, and 1532 nm). The stability of the optical system was improved by the common optical path formed by time-division multiplexing (TDM) technology. The calibration experiments show that the second harmonics and the concentrations of the six gases are linear. A comparison experiment with gas chromatography (GC) demonstrates that the error of acetylene reaches the nL/L level, while the other gases reach the μL/L level. The data conforms to the power industry testing standards, and the state of the transformer is analyzed by the detected six characteristic gases. The setup provides an effective basis for the online detection of dissolved gas in transformer insulating oil.

A reconfigurable and compact hardware architecture of CLEFIA block cipher with multi-configuration

In this paper, a reconfigurable architecture of CLEFIA block cipher which supports multi-configuration is proposed. Moreover, different generalized Feistel networks are integrated into a novel folding structure, which not only increases the circuit flexibility but also reduces the hardware overhead. Besides, the processes of generating intermediate key and encryption share the same circuit by time-division multiplexing technology to reduce the hardware resource consumption further. The proposed CLEFIA design is implemented in Artix-7 XC7A35 T FPGA board. Measurement results show that it can realize all the three CLEFIA configurations of key size, which are 128/192/256-bit, with a few resources of 1725 look-up-tables and 663 registers. At a clock frequency of 147 MHz, it also reaches high throughputs of 990 Mbps, 818 Mbps, and 696 Mbps in the three configurations respectively.

Optical access network interfaces for 5G and beyond [Invited

Point to point (PtP), wavelength division multiplexing (WDM) and time division multiplexing (TDM) optical interfaces are discussed as solutions for backhaul, midhaul, and fronthaul networks. The evolution of radio access networks (RANs) for 5G and beyond is introduced and PtP is identified as the most deployed solution, with many transceiver technologies available to cover the different needs for each RAN configuration. WDM and TDM interfaces remain of interest when a lack of fiber occurs. WDM technologies are being adapted to answer to this RAN market with the appearance of medium-WDM (MWDM) and autotunable dense-WDM (DWDM) transceivers. TDM technologies are trying to evolve towards higher bit rates and lower latency to cope with RAN backhaul specifications. A gap in the transceiver technologies is identified for each of those interface types and also for bit rates above 25 Gbit/s that will impose more complex optics, electronics, and integration.

Application of TDM and FDM methods in TDLAS based multi-gas detection

Multi-gas tunable diode laser absorption spectroscopy (TDLAS) system based on time division multiplexing (TDM) demodulation technology which combine with frequency division multiplexing (FDM) technology is proposed, called F-TDM (frequency- time division multiplexing) system. In addition, traditional TDM technology and FDM technology are introduced to analyze and compare their performance. As for the performance of F-TDM system, multi-gas detection of CH4 and C2H2 has been accomplished with minimum detection limits of 10.24 ppmv for CH4 at 1653.72 nm and 0.763 ppmv for C2H2 at 1532.83 nm respectively. The relationships (CH4: R-square = 0.9989; C2H2: R-square = 0.9995) between gas concentration and second harmonic signal amplitude are proved as a good linear response. It is consistent with the data obtained by traditional TDM and FDM demodulation methods, indicating that the F-TDM system is feasible. By comparison, it is known that different methods have their advantages in different applications. The TDM system uses less equipment and is the most cost-effective. The system based on FDM technology is the most time-saving. The F-TDM system is a compromise method that combines the advantages of both and has no obvious disadvantage at the detection limit.

Chirped-apodized Thue-Morse quasiperiodic structures for multichannel optical dispersion compensation

Nowadays, optical data transmission systems are significantly involved in telecommunication networks. Particularly, hundreds of data channels can be sent concurrently over a single optical fiber through dense wavelength division multiplexing (DWDM) and optical time division multiplexing technologies. Nevertheless, dispersion imposes main limitations for having high capacity systems with high transmission rates. This paper suggests a new dispersion compensating scheme by introducing one-dimensional chirped and apodized Thue-Morse quasiperiodic structures. Numerical investigations of the dispersion features of the proposed structure is presented. According to the acquired relatively smooth and negative slope group delay (GD) along with corresponding negative constant group velocity dispersion (GVD) of the reflection bands, it would be possible to apply the suggested structure in an efficient way in DWDM applications for multiband dispersion compensation in optical communication systems. The designed multilayer structure with short physical length and ultrahigh negative dispersion coefficient and with the free spectral range (FSR) of about 0.8 nm meets the International Telecommunication Union-Telecommunication Standardization (ITU-T) Sector requirements. Besides, the impact of main structural design parameters on the spectral features of the suggested system are presented in this paper.

A QoE-Aware Energy Supply Scheme over a FiWi Access Network in the 5G Era.

Integrated fiber-wireless (FiWi) should be regarded as a promising access network architecture in future 5G networks, and beyond; this due to its seamless combination of flexibility, ubiquity, mobility of the wireless mesh network (WMN) frontend with a large capacity, high bandwidth, strong robustness in time, and a wavelength-division multiplexed passive optical network (TWDM-PON) backhaul. However, the key issue in both traditional human-to-human (H2H) traffic and emerging Tactile Internet is the energy conservation network operation. Therefore, a power-saving method should be instrumental in the wireless retransmission-enabled architecture design. Toward this end, this paper firstly proposes a novel energy-supply paradigm of the FiWi converged network infrastructure, i.e., the emerging power over fiber (PoF) technology instead of an external power supply. Then, the existing time-division multiplexing access (TDMA) scheme and PoF technology are leveraged to carry out joint dynamic bandwidth allocation (DBA) and provide enough power for the sleep schedule in each integrated optical network unit mesh portal point (ONU-MPP) branch. Additionally, the correlation between the transmitted optical power of the optical line terminal (OLT) and the quality of experience (QoE) guarantee caused by multiple hops in the wireless frontend is taken into consideration in detail. The research results prove that the envisioned paradigm can significantly reduce the energy consumption of the whole FiWi system while satisfying the average delay constraints, thus providing enough survivability for multimode optical fiber.

Dual-View Integral Imaging System With Wide Viewing Angle And High Spatial Resolution

In this paper, a dual-view integral imaging system is proposed to present two different 3D images for viewers in different viewing zones. For most of the conventional dual-view integral imaging systems, either the viewing angle or the spatial resolution of 3D image is decreased. In the proposed dual-view system, the viewing angle of each viewing zone is enlarged by introducing a switchable mask. Meanwhile, the spatial resolution of the 3D image is maintained by using the time-division multiplexing technology. A prototype of the proposed dual-view system is developed and it has wide viewing angle and high spatial resolution. The experiments coincide with the theoretical analysis.

A high-sensitivity multilayer soil moisture monitoring sensor based on a double high-frequency tuning detection circuit

The multilayer soil moisture Internet of things sensor is designed to monitor the moisture of multiple soil profiles in real time. Its sensitivity and accuracy are of great concern to improve the performance of sensors. This article introduces the system composition of the end-cloud integrated multilayer soil moisture Internet of things sensor and then focuses on the design of key technologies, such as the moisture detection circuit, the time division multiplexing detection technology, and the deredundancy circuit in the analog–digital integrated design. The performance of the soil moisture detection circuit is directly related to the measurement accuracy of the sensor. A detection method is proposed using a high-frequency double-resonance circuit, which can detect small changes in moisture by changing the circuit detuning voltage. The maximum root mean square error of the calibration is less than 1.35% for five typical soils from different places. Compared with that of an independent detection method, the output consistency of the time division multiplexing detection is significantly improved by using the time division multiplexing detection method, which has a root mean square error of only 0.12%. In order to reduce errors caused by inconsistency in each burial, the gravimetric analysis is used in the sensitivity monitoring test, which shows that small changes in soil moisture can be detected by the circuit.

Application of high-resolution autostereoscopic display for medical purposes

In this paper we propose an application of high-resolution autostereoscopic display for medical purposes. To realize high resolution autostereoscopy for medical applications, we use timedivision multiplexing parallax barrier technology. Moreover, we evaluate the merit of using the autostereoscopic display we propose based on subjective experiments. From the results of the subjective experiments, we find out that 3D image is perceived to have a higher resolution compared with the 2D image.

Two-component gas quartz-enhanced photoacoustic spectroscopy sensor based on time-division multiplexing of distributed-feedback laser driver current.

A two-component gas sensor in quartz-enhanced photoacoustic spectroscopy based on time-division multiplexing (TDM) technology of a distributed-feedback (DFB) laser driver current was proposed and experimentally demonstrated. The quartz tuning-fork-based photoacoustic spectroscopy (PAS) cell configuration with two optical collimators and two acoustic microresonators was designed to detect the second-harmonic (${2}f$2f) PAS signal. The two optical collimators guaranteed that the two laser beams would inject the PAS cell conveniently, providing higher power input than a 3 dB optical fiber coupler. Two-component gas sensing was achieved by the TDM of the DFB laser driver current. We used this two-component gas sensing technique to detect acetylene (${{\rm C}_2}{{\rm H}_2}$C2H2) at 1532.83 nm and methane (${{\rm CH}_4}$CH4) at 1653.722 nm. The ${{\rm C}_2}{{\rm H}_2}$C2H2 and ${{\rm CH}_4}$CH4 detection was achieved at a 2.4 s interval. The minimum detection limits of 1 ppmv for ${{\rm C}_2}{{\rm H}_2}$C2H2 and 13.14 ppmv for ${{\rm CH}_4}$CH4 were obtained, and the linear responses reached were 0.99968 and 0.99652 for ${{\rm C}_2}{{\rm H}_2}$C2H2 and ${{\rm CH}_4}$CH4, respectively. Moreover, the continuous monitoring of ${{\rm CH}_4}$CH4 and ${{\rm C}_2}{{\rm H}_2}$C2H2 for 40 min showed a good stability. The TDM technology of the DFB laser driver current would play an important role on the multi-component detection.

SD‐MAC: Design and evaluation of a software‐defined passive optical intrarack network in data centers

AbstractWith rapid development of cloud computing services, traffic in data centers (DCs) increases dramatically. Top‐of‐rack Ethernet switches dominate network cost and energy consumptions in DCs. Optical switching technologies have been introduced into DC networks to increase switching capacity and to reduce energy consumption. However, how to design high‐performance optical intrarack networks is still a great challenge. This paper presents a software‐defined passive optical intrarack network (SD‐POIRN) based on optical coupler fabrics. The data plane of SD‐POIRN is a broadcast‐and‐select optical network combining wavelength division multiplexing and time division multiplexing technologies. The control plane of SD‐POIRN has a centralized rack controller for scheduling intrarack data transmissions. This paper proposes a software‐defined media access control (SD‐MAC) protocol for SD‐POIRN. The SD‐MAC utilizes dynamic transmission and receiving server grouping methods and max‐min fair share bandwidth allocation algorithms to dynamically allocate bandwidth among servers in an efficient and fair manner. Network performance evaluation results show that, when the offered load is high, the proposed SD‐MAC protocol effectively increases network throughput and reduces average packet delay compared with previous works.

An MIMO Radar System Based on the Sparse-Array and Its Frequency Migration Calibration Method

In this paper, a Multiple Input Multiple Output (MIMO) radar system based on a sparse-array is proposed. In order to reduce the side-lobe level, a genetic algorithm (GA) is used to optimize the array arrangement. To reduce the complexity of the system, time-division multiplexing (TDM) technology is adopted. Since the signals are received in different periods, a frequency migration will emerge if the target is in motion, which will lead to the lower direction-of-arrival (DOA) performance of the system. To solve this problem, a stretching transformation method in the fast-frequency slow-time domain is proposed, in order to eliminate frequency migration. Only minor adjustments need to be implemented for the signal processing, and the root-mean-square error (RMSE) of the DOA estimation will be reduced by about 90%, compared with the one of an uncalibrated system. For example, a uniform linear array (ULA) MIMO system with 2 transmitters and 20 receivers can be replaced by the proposed system with 2 transmitters and 12 receivers, achieving the same DOA performance. The calibration formulations are given, and the simulation results of the automotive radar system are also provided, which validate the theory.

Multi-Component and Multi-Point Trace Gas Sensing in Wavelength Modulation Spectroscopy Based on Wavelength Stabilization

Multi-component and multi-point trace gas sensing in the wavelength modulation spectroscopy is demonstrated based on the frequency-division multiplexing and time-division multiplexing technology. A reference photodetector is connected in series with a reference gas cell with the constant concentration to measure the second-harmonics peak of the components for wavelength stabilization in real time. The central wavelengths of the distributed feedback lasers are locked to the target gas absorption centers by the reference second-harmonics signal using a digital proportional-integral-derivative controller. The distributed feedback lasers with different wavelengths and modulation frequencies are injected into the gas cell to achieve multi-components gas measurement by the frequency-division multiplexing technology. In addition, multi-point trace gas sensing is achieved by the time-division multiplexing technology using a photoswitch and a relay unit. We use this scheme to detect methane (CH4) at 1650.9 nm and water vapor (H2O) at 1368.597 nm as a proof of principle with the gas cell path length of 10 cm. The minimum detection limits achieved for H2O and CH4 are 1.13 ppm and 11.85 ppm respectively, with three-point gas cell measurement; thus 10.5-fold and 10.1-fold improvements are achieved in comparison with the traditional wavelength modulation spectroscopy. Meanwhile, their excellent R-square values reach 0.9983 and 0.99564 for the concentration ranges of 500 ppm to 2000 ppm and 800 ppm to 2700 ppm, respectively.

Field Comparison Tests of LDM and TDM in ATSC 3.0

In this paper, we present laboratory and field test results of layered division multiplexing (LDM) and time division multiplexing (TDM) technologies based on Advanced Television Systems Committee 3.0. The presented field test results include analysis in several scenarios such as rooftop, indoor, and mobile receptions. In order to provide performance comparison of the LDM and TDM technologies, reception power (field strength) and successful reception rate are measured for all the considered scenarios. For in-depth analysis in real field environment, further field measurements such as threshold of visibility, marginal (minimal) reception power, and erroneous second ratio are used for rooftop, indoor, and mobile receptions, respectively. The laboratory and field test results show that the LDM technology not only shows superior performance compared to the TDM technology in all the considered scenarios (rooftop, indoor, and mobile receptions), but also enables broadcaster to efficiently provide a variety of services (e.g., mobile, pedestrian, indoor, and stationary services) with different robustness within a single radio frequency channel.

RETRACTED: Study of a novel distributed vibration sensing system based on weak fiber Bragg gratings

A novel vibration sensing system based on distributed weak fiber Bragg gratings is demonstrated to overcome the drawbacks of the conventional methods used in optical fiber sensing networking, such as insufficient quantity of multiplexed fiber Bragg gratings in wavelength-division multiplexing systems and low signal intensity in conventional time-division multiplexing systems. By mixing wavelength-division multiplexing technology and time-division multiplexing technology, the physical parameters of the fiber Bragg grating locations can be measured, but the distributed measurement along the whole optical fiber cannot be realized. The proposed novel sensing system detects the vibration events along the optical fiber link according to the signal’s intensity interference variation caused by the reflected signals with the adjacent weak fiber Bragg gratings. The position of the vibration events can be accurately determined by using time-division multiplexing technology. The experimental results verify that this novel system is more convenient for realizing vibration detection and demodulation along the whole optical fiber than before, and the system locating accuracy can be up to 20.5 m, with the capability of detecting various signals with 0.2 V of the driven signals as the bottom limit of voltage and a frequency range from 3 to 1000 Hz.

On-chip generation of time-and wavelength-division multiplexed multiple time-bin entanglement.

Optical quantum states based on entangled photons are the key resource in quantum-information science. The realization of multiplexed multiple entanglement are necessary for developing high-capacity quantum information process. Silicon-on-insulator (SOI) has recently become a leading platform for generating and processing of non-classical optical states. In this work, by combining the wavelength- and time-division multiplexing technologies, we demonstrate a multiplexing time-bin entangled photon pair source based on a silicon nanowire waveguide and distribute entangled photons into 3(time) × 14(wavelength) channels independently. The indistinguishability of photon pairs in each time channel is confirmed by a fourfold Hong-Ou-Mandal quantum interference. Our work paves a new and promising way to achieve a high capacity quantum communication and to generate a multiple-photon non-classical state.

Integrated High-Speed Optical SerDes over 100GBd Based on Optical Time Division Multiplexing

An on-chip optical transceiver for transmission system over 100GBd is proposed based on optical time division multiplexing (OTDM) technology, and the performances, such as the insertion loss, the inter-symbol interference (ISI) crosstalk, and the potential symbol rate, are analyzed in detail. Co-designed with the double rail driver, on-chip Mach-Zehnder interferometer switch repeatedly generates extremely narrow sampling pulses of only 12ps full width at half maximum. Based on such narrow optical sampling pulse train, a four-stage cascaded optical switch divides the 25GHz clock cycle into four recurrent 9.5ps time slots and one blank time slot of 2ps. Thus, a 100GBd optical transmission channel is realized based on 4-bit 25Gbps bit-streams at the electrical interface. The ISI extinction ratio at the worst channel is 1.9dB with 10dB depth modulator, and the insertion loss caused by the OTDM mechanism is about 16dB. Further, taking advantages of dark modulation, an OTDM system with 5-bit 25Gbps bit-streams at the electrical interface is proposed to generate a 125GBd transmission utilizing the same optical sampling pulse. The ISI performance is much better and the extinction ratio at the worst channel is enhanced to 3.99dB.

Distributed Weak Fiber Bragg Grating Vibration Sensing System Based on 3 \xd7 3 Fiber Coupler

A novel distributed weak fiber Bragg gratings (FBGs) vibration sensing system has been designed to overcome the disadvantages of the conventional methods for optical fiber sensing networking, which are: low signal intensity in the usually adopted time-division multiplexing (TDM) technology, insufficient quantity of multiplexed FBGs in the wavelength-division multiplexing (WDM) technology, and that the mixed WDM/TDM technology measures only the physical parameters of the FBG locations but cannot perform distributed measurement over the whole optical fiber. This novel system determines vibration events in the optical fiber line according to the intensity variation of the interference signals between the adjacent weak FBG reflected signals and locates the vibration points accurately using the TDM technology. It has been proven by tests that this system performs vibration signal detection and demodulation in a way more convenient than the conventional methods for the optical fiber sensing system. It also measures over the whole optical fiber, therefore, distributed measurement is fulfilled, and the system locating accuracy is up to 20 m, capable of detecting any signals of whose drive signals lower limit voltage is 0.2 V while the frequency range is 3 Hz‒1 000 Hz. The system has the great practical significance and application value for perimeter surveillance systems.

A Thermal-Aware Power Allocation Method for Optical Network-on-Chip

Optical network on chip (ONoC) is a promising on-chip communication architecture for future many-core systems due to its high performance and energy efficient. ONoC is mostly constructed with microring resonators. However, thermo-optic effect will lead to the drift of the operation point and ultimately have a serious impact on the signal-to-noise rate (SNR). In order to solve this problem, a thermal-aware power allocation method is proposed in this paper. Every communication request should be provided with enough power to satisfy the minimum SNR requirement. Time division multiplexing technology is adopted to solve the power allocation conflicts and communication path conflicts in the network. In order to minimize the number of slots satisfying the rated power supply, an optimization model is established and solved. The simulation results indicate that our proposed method can increase the success rate of communication requests from an average of 43% to 100% in four different on-chip thermal distribution scenarios when compared with four communication scenarios without optimization. It also saves 66.7% of the laser power in average compared with the traditional power allocation method.